[R-sig-ME] interaction terms interpretation

Mon Aug 10 16:58:58 CEST 2015

Thankyou Ben! It looks great. Cheers
El 10/08/2015 11:54, "Ben Bolker" <bbolker at gmail.com> escribió:

> Consider taking a look at
> http://ms.mcmaster.ca/~bolker/R/misc/foxchapter/bolker_chap.html .
>
> On Mon, Aug 10, 2015 at 10:30 AM, Joaquín Aldabe
> <joaquin.aldabe at gmail.com> wrote:
> > Thankyoy very much Ken and Thierry. I'll try that. Is there any specific
> > function for making graphs of the model? I appreciate recommendations or
> > citations to explore how to graph model results. Thanks again. Joaquin
> > El 10/08/2015 07:36, "Ken Beath" <ken.beath at mq.edu.au> escribió:
> >
> >> There is actually a continuous third order interaction, which are just
> >> about impossible to interpret.
> >>
> >> As well as the graphs, which you always should start with, think about
> >> what is sensible for the model. Should any of the predictors be
> log-scaled?
> >> As AMGP is a count it wouldn't be surprising it it is, or use log(1+x)
> if
> >> there are zeroes.
> >>
> >> Look at diagnostic plots and make sure that everything is fine,
> especially
> >> that there are no outliers which might be causing the interaction.
> >>
> >> Ken
> >>
> >> On 10 August 2015 at 17:02, Thierry Onkelinx <thierry.onkelinx at inbo.be>
> >> wrote:
> >>
> >>> Dear Joaquin,
> >>>
> >>> Your mail is mangled because you send it in HTML. This makes the model
> >>> output very hard to read.
> >>>
> >>> It's impossible to interpret model output without thorough knowledge of
> >>> the
> >>> dataset. I suggest that you try to make some graphs of the model.
> >>>
> >>> Best regards,
> >>>
> >>> ir. Thierry Onkelinx
> >>> Instituut voor natuur- en bosonderzoek / Research Institute for Nature
> and
> >>> Forest
> >>> team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
> >>> Kliniekstraat 25
> >>> 1070 Anderlecht
> >>> Belgium
> >>>
> >>> To call in the statistician after the experiment is done may be no more
> >>> than asking him to perform a post-mortem examination: he may be able to
> >>> say
> >>> what the experiment died of. ~ Sir Ronald Aylmer Fisher
> >>> The plural of anecdote is not data. ~ Roger Brinner
> >>> The combination of some data and an aching desire for an answer does
> not
> >>> ensure that a reasonable answer can be extracted from a given body of
> >>> data.
> >>> ~ John Tukey
> >>>
> >>> 2015-08-07 21:27 GMT+02:00 Joaquín Aldabe <joaquin.aldabe at gmail.com>:
> >>>
> >>> > Hi all, I´m running a mixed model with poisson error distribution as
> I
> >>> have
> >>> > count data of a shorebird species. My predictors are AMGP (another
> >>> > shorebird that is usually associated to "my" species and probably has
> >>> > ecological influence on it), grass height and field distance to the
> >>> lagoon.
> >>> >
> >>> > I´m having a hard time trying to interpret second order
> interactions. I
> >>> > appreciate your comments of references recommendations. Here is the
> >>> output
> >>> > of my model. All the best, Joaquín.
> >>> >
> >>> > Call:glmmadmb(formula = BBSA ~ AMGP * Grass_height *
> >>> > Distance_to_lagoon +     (1 | Field_name) +
> offset(log(Field_area.o)),
> >>> > data = my4S,     family = "nbinom1", zeroInflation = TRUE)
> >>> > AIC: 226
> >>> > Coefficients:                                     Estimate Std. Error
> >>> > z value Pr(>|z|)    (Intercept)                           -5.8797
> >>> > 1.2250   -4.80  1.6e-06 ***AMGP
> >>> > 3.3086     1.0246    3.23   0.0012 ** Grass_height
> >>> >      -4.1592     1.9961   -2.08   0.0372 *  Distance_to_lagoon
> >>> >            -0.5029     1.3929   -0.36   0.7180    AMGP:Grass_height
> >>> >                   2.9442     1.5142    1.94   0.0518 .
> >>> > AMGP:Distance_to_lagoon               -2.4695     0.9632   -2.56
> >>> > 0.0104 *  Grass_height:Distance_to_lagoon        0.0339     2.0065
> >>> > 0.02   0.9865    AMGP:Grass_height:Distance_to_lagoon  -4.0363
> >>> > 1.3264   -3.04   0.0023 ** ---Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01
> >>> > ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
> >>> > Number of observations: total=64, Field_name=16 Random effect
> >>> > variance(s):Group=Field_name            Variance StdDev(Intercept)
> >>> > 0.03721 0.1929
> >>> > Negative binomial dispersion parameter: 20.633 (std. err.:
> >>> > 7.4042)Zero-inflation: 1e-06  (std. err.:  6.8336e-09 )
> >>> > Log-likelihood: -102
> >>> >
> >>> >
> >>> > --
> >>> > *Joaquín Aldabe*
> >>> >
> >>> > *Grupo Biodiversidad, Ambiente y Sociedad*
> >>> > Centro Universitario de la Región Este, Universidad de la República
> >>> > Ruta 15 (y Ruta 9), Km 28.500, Departamento de Rocha
> >>> >
> >>> > *Departamento de Conservación*
> >>> > Aves Uruguay
> >>> > BirdLife International
> >>> > Canelones 1164, Montevideo
> >>> >
> >>> > https://sites.google.com/site/joaquin.aldabe
> >>> > <https://sites.google.com/site/perfilprofesionaljoaquinaldabe>
> >>> >
> >>> >         [[alternative HTML version deleted]]
> >>> >
> >>> > _______________________________________________
> >>> > R-sig-mixed-models at r-project.org mailing list
> >>> > https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
> >>> >
> >>>
> >>>         [[alternative HTML version deleted]]
> >>>
> >>> _______________________________________________
> >>> R-sig-mixed-models at r-project.org mailing list
> >>> https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
> >>>
> >>
> >>
> >>
> >> --
> >>
> >> *Ken Beath*
> >> Lecturer
> >> Statistics Department
> >> MACQUARIE UNIVERSITY NSW 2109, Australia
> >>
> >> Phone: +61 (0)2 9850 8516
> >>
> >> Level 2, AHH
> >> http://stat.mq.edu.au/our_staff/staff_-_alphabetical/staff/beath,_ken/
> >>
> >> CRICOS Provider No 00002J
> >> This message is intended for the addressee named and m...{{dropped:12}}
> >
> > _______________________________________________
> > R-sig-mixed-models at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
>

	[[alternative HTML version deleted]]